The galvanic cell has become a primary power source for many portable electronic devices such as tape recorders, portable telephones, lanterns, radios and the like. In order to maintain the overall electronic devices as compact as possible, the electronic devices are usually designed with cavities to accommodate batteries as their power source. The cavities are usually made so that a battery can be snugly positioned therein, thus making electronic contact with appropriate terminals within the device. To accommodate the electronic component manufacturers, the battery industry has adapted several conventional size cells which the manufacturers can rely upon in designing their devices which require portable power sources. Due to the large number of battery-powered devices on the market, there has been a demand for increased power output capacities of standard size cells. Accordingly, various cell constructions have been employed so as to provide a sufficient output capacity. For example, cells with coiled electrode assemblies (jellyroll construction) have been used to increase the intefacial area contact between the active cell components. Use of coiled electrodes serves to decrease the cell's internal resistance and thereby increase the maximum possible drain rates. Cells that incorporate a jellyroll construction are widely known in the battery art and usually involve placement of the coiled electrode in a composite housing which serves as the current conductive terminals for the cell. In such structures, the electrode of one polarity can be electrically connected to a conductive housing portion, and the electrode of the opposite polarity can be generally electrically connected to another conductive housing portion which is insulated relative to the electrically conductive first-mentioned housing portion. The electrical contact between each electrode and its respective housing portion is generally formed by an elongated flexible electrically conductive connecting tab (current collector tab) or element which is secured at one end to the electrode and at the other end is secured to the respective housing portion. The current collector tabs are generally attached to the electrodes or electrode carriers, by welding, pressure contact or other conventional means. This technigue requires time-consuming manual operations (in the cell assembly process) which serves to reduce line productivity and add to the manufacturing costs. For example, some of the problems associated with using this method of tabbing are: (1) the obvious difficulty of handling and welding narrow strips of metal within the confined space of the cell; (2) dedicating a disproportionate percentage of the volume within the cell to accommodate the tab and assembly process; (3) the tab is connected to the electrode in only one spot and therefore it is possible that any bulging of the cell could break the weld causing an open circuit; and (4) coil insertion is difficult due to the ease with which the electrodes and/or separator may be damaged.
U.S. Pat. No. 3,505,121 discloses a procedure for substantially uniformly welding current collectors to protruding edges of respective opposite polarity electrodes assembled as a winding or block of such electrodes wherein the edges of opposite polarity electrodes protrude from opposite ends of the winding or block. The procedure comprises applying plate-like members of a collector unit to cover portions of such protruding edges and also applying a counter welding electrode to portions of edges of such protruding electrodes not covered by and adjacent the portions covered by said members and applying a welding electrode to such members and passing welding current between the welding and counter welding electrodes so as to weld the members to the edge portions of the electrodes in the winding or block covered thereby said current which is uniformly distributed by the disposition of said welding and counter-welding electrodes relative to each other. The collector plate members may have maltese cross-like shape and the counter electrodes complementary shape to fit into spaces between rays of the cross. Other shapes may be given to said plate-like members and to said counter electrodes.
U.S. Pat. No. 3,503,806 discloses a cell construction in which the negative plate edges extend longitudinally beyond the positive plate edges in one direction and the positive plate edges extend longitudinally beyond the negative plate edges in the opposite direction. Terminal straps are attached to the extending edges of the plates at a plurality of points. The plates may be spirally wound and the negative plate connected to a conductive casing through one terminal strap and the positive plate connected to terminal rivet through the remaining terminal strap. As a separate or combined feature a resilient washer having a durometer rating the range of from 15 to 95 may be positioned adjacent either or both ends of the plates.
It is an object of the present invention to provide a method for assembling coiled electrodes into a cell housing that is cost effective and suitable for automatic assembly operations.
It is another object of the present invention to provide a novel method for assembling a cell with coiled electrodes.
It is another object of the present invention to provide a method for assembling coiled electrodes into a cell housing in which each coiled electrode extends beyond a different end of the coiled electrode assembly and is secured to a conductive tab such that multiple edge electrode contact points are made with the tab.
The foregoing and additional objects will become fully apparent from the following description and the accompanying drawings.